The present application relates to an optical recording medium, especially to an optical recording medium by which a detection or rejection of an illegal replica-version can be performed effectively.
An optical disc as an optical recording medium, especially a ROM (Read Only Memory) disc of playback-only is widely used in the world as a package-media, because a lot of replica substrate can be produced from one stumper in the short time by an injection forming of plastic.
For example, a CD (Compact Disc), DVD (Digital Versatile Disc) and the like are common in the market as the ROM disc that music, picture and the like are recorded to.
From the past, on the basis of the ROM disc that is sold as a package-media, a disc of replica-version (so-called pirate's version) that copied the recorded data illegally is produced and, that causes a problem of the infringement of the copyright.
As for the disc of pirate's version, generally, a stumper is produced by a mastering process on the basis of a signal reproduced from a normal version disc and thereby producing the disc of replica-version.
Alternatively, it is produced by copying the signal reproduced from the normal version disc, to a recordable disc.
In order to prevent the production of the disc of pirate's version, varieties of methods are proposed and developed. As one of methods, for example, a method by which different identity information is added to each disc is known. A system in which a reproducing apparatus side reads out the identity information of the disc and transmits this to an outside server apparatus via a network can be configured by using the method by which different identity information is added to each disc, like this. By using such system, for example, because the same identity information is detected voluminously by aforesaid server apparatus when the disc of pirate's version are produced and sold, the presence of the discs of pirate's version can be detected. Further, by specifying a reproducing apparatus which transmitted the detected identity information, there is a possibility to be able to specify a seller of pirate's version.
However, even if the identity information that becomes unique is added to each disc, like this, that it is recorded by a method by which the reproduction or copying may not be performed easily by a driving apparatus sold in the market is useful for the protection of the copyright.
Then, a mark of aforesaid identity information is formed on a reflective film of the disc and a very small change of the reflection ratio is given, a method in which the recording is performed by using that is proposed (for example, reference to Patent document 1).
In a disc described in this patent document 1, main data (data of contents, control information or the like) are recorded by a combination of pit and land, and also sub-data (identity information) other than the main data are recorded by forming a mark that gives a very small change of the reflectance to the reflective film on a specified pit and land.
The recording of the mark for the aforesaid reflective film is performed by a laser irradiation whose power is higher than a laser power of the time of reproducing. At this time, the change of the reflectance is made to be very small so that it may not give an influence to the reproducing of main data that are recorded by the combination of pit and land. More specifically, it is done such that the sub-data are not reproduced by the usual reproducing action of the main data.
Then, another reproducing system is provided, and many portions where such very small change of the reflectance is given in the reproducing signal of main data are sampled by sampling, and for example, by obtaining an integrated value of these, the reproduction of this sub-data itself is performed.
In this case, at a recording apparatus side and reproducing apparatus side of the sub-data, the position where the mark as the sub-data is formed is determined by the predetermined specified algorithm. By means of this, the normal reproducing apparatus can specify the position where the mark was recorded by the same algorithm as the one that was used when recording, thereby being able to reproduce the identity information as the sub-data correctly.
And now, it was assumed that the pirate's version disc is produced from the reproducing signal of the ROM disc of normal version, but there is a method, as another method, in which a stumper is made by copying a physical shape of substrate of the ROM disc, as it is.
Specifically, first, shapes of pits and lands that were formed on the substrate are exposed by separating the cover layer and reflective film of the normal version disc from the substrate, and this exposed concavity/convexity is copied physically, thereby copying the contents recorded on the disc and, this is the method.
The disc described in the aforesaid patent document 1 is the one which records the identity information of the individual disc by the mark formed to the reflective film. According to this, by the method of the physical copy which needs to remove the cover layer and reflective film from the aforesaid substrate, the mark (identity information) formed to the reflective film may not be copied, therefore it is conceivable that the production of the pirate's version disc may be protected.
However, practically, the record of the mark to the reflective film is performed by the irradiation of the comparatively high power laser, therefore, at the time of recording the intended mark, it may cause problems such as: the temperature of this recording portion increases, thereby causing local thermal expansion to the disc's substrate; the transformation corresponding to the mark is caused to the substrate itself and the like.
Consequently, the mark to be formed only to the reflective film may be copied to the substrate physically, and by copying this substrate physically, the main data and also sub-data may be copied.
It is explained with respect to this copy with reference to next FIG. 24.
FIG. 24A is a sectional structure of an optical disc 100 in which a mark was formed to a reflective film as doing like the above.
This optical disc 100 is formed with reflective film 102 and cover layer 103 at least on a substrate 101. Then, the concave/convex sectional shape formed between the substrate 101 and the reflective film 102 is the portion where main data is recorded by the combination of pit and land.
Also, as is mentioned above, the mark as sub-data is recorded to the reflection layer on the specified pit or land, as shown with numeral X. In the figure, an example in which the mark (X) is recorded to the reflective film 102 on the specified land is shown.
In addition, as for the naming of land in this description, the shaped portion that is optically near to the source of light by which the light is inputted to the concave/convex surface, in the concave/convex surface on the optical recording medium of the optical disc or the like, namely the shaped portion that is the convexity toward the light incident side is called “Land”.
In this case, as is mentioned above, at the time of recording of the mark as the sub-data, because the comparative high power laser is irradiated to the reflective film 102, there is possibility that the transformation by the thermal expansion according to the increase of temperature is caused at the portion (X) where the mark is formed. According to this transformation, the hollow of the concave shape is copied to the surface that touches the reflective film 102 of the substrate 101. Consequently, in this case, when the cover layer 103 and the reflective film 102 are removed and the substrate 101 is exposed, it becomes the one in which the concave shape corresponding to the mark that is formed only to the reflective layer 102 was copied to the surface of the substrate 101, as is shown in FIG. 24B.
The concave shaped portion that was copied like this becomes portions where the reflective rate decreases slightly in comparison with the other land portions. Consequently, in a replica substrate to which the concave shape of such substrate 101 is copied as it is and made, it becomes the one that reproduced the mark as sub-data as it is.
Then, when the reflective film and the cover layer are stacked and formed on such replica substrate in the same process as the usual manufacturing process, the pirate's version disc where the main data and sub-data that were recorded on the normal version disc were completely copied may be manufactured.
Patent document 1: Japanese registered patent No. 3454410.
On the other hand, previously, by a Japanese patent application No. 2005-205439 (patent application according to claim of priority on the basis of a Japanese patent application 2005-30272), applicants proposed a reproduction apparatus, reproducing method, recording method, recording method, manufacturing method of optical disc and an optical disc recording medium. By means of those, the reproduction that differs from the normal version of polarity inversion or the like is performed to the so-called pirate's version's optical recording medium by the unauthorized replica, even if copy protection or physical copy of sub-data for detection occurred, as is mentioned above.